Cactus craziness

My book will be called "The Cactus Eaters.'' It will be coming out next year, and the book has required me to do a lot of research about cacti. The book is not about cacti per se, but a cactus figures prominently in one very painful backcountry scene that takes place about a quarter of the way through, in the middle of the desert. For this reason, I've been looking for all kinds of ephemera and weird facts about cacti. My wife dug up a great piece of information: she found a document that suggested that a prickly pear cactus caused a shocking international incident in California about a half-century ago )I won't go into any more details -- you'll have to read the book to see exactly what happened.) I also found out that Aztec priests used cactus spines to scourge themselves as part of a painful-sounding purification ritual. Anyone with other strange cactus facts: please post them here.